1. Field of the Invention
The present invention relates to a seat track for vehicles, and more particularly to a seat track comprising a fixed rail, and a movable rail used to move a seat back and forth, which have a structure of enabling a pin type locking device to be mounted thereto, thereby increasing resistance to shock applied from the front or rear side thereof, and of eliminating a bead forming process, which was inevitably performed in the prior art, thereby improving workability, resulting in a minimization of manufacturing costs.
2. Description of the Related Art
In general, seats for vehicles are configured to move back and forth within a predetermined extent in order to secure optimum ride comfort of drivers and passengers. With such configuration of seats, especially, drivers can adjust the position of their seats on the basis of his/her body size, thereby enabling to operate a steering wheel or pedal in the most comfortable sitting posture.
Referring to FIGS. 4 and 5 illustrating a conventional seat track, it comprises a fixed rail 100, a movable rail 200, and a plurality of rollers or balls 300. The fixed rail 100 is fastened to the bottom plane of a vehicle body by using bolts so as not to move, and the movable rail 200 is fitted into the fixed rail 100 so that it is positioned in the upper portion of the fixed rail 100 and adapted to move back and forth in a state wherein a seat for a vehicle is mounted on the upper surface thereof. Between the fixed rail 100 and movable rail 200 there are provided the balls 300 for allowing the movable rail 200 to smoothly move relative to the fixed rail 100 in a state wherein they face each other.
The fixed rail 100 of the conventional seat track comprises a horizontal bottom fixed piece 110, a pair of vertical pieces 120 formed by upwardly bending both side portions of the fixed piece 110 at a right angle, a pair of grooves 130 formed by rounding the center portion of each of the vertical pieces 120 to have an outwardly convex semi-circular form for allowing the balls 300 to be inserted therein, and a pair of U-shaped end pieces 140 formed by downwardly bending the end portion of each of the vertical pieces 120 at a right angle to have a reversed U-shaped form. The fixed piece 110 is centrally formed at one side thereof with a bead portion 111 as an upwardly protruded portion, and in turn, a plurality of fitting holes 112 are formed along a center axis of the bead portion 111 so that they are spaced apart from one another by constant distances.
The movable rail 200 of the conventional seat track comprises a seat mounting portion 210, a pair of vertical walls 220 formed by downwardly bending both side portions of the seat mounting portion 210 at a right angle, a pair of grooves 230 formed by upwardly bending the end portion of each of the vertical walls 220 so as to have a U-shaped form and rounding the center of the bent portion for allowing the balls 300 to be inserted therein at the same position as the grooves 130 of the fixed rail 100, and a pair of flanges 240 formed as vertical edge regions of the grooves 230. The seat mounting portion 210 has a width slightly narrower than that of the fixed piece 110 of the fixed rail 100, and is coupled at the upper surface thereof to a seat.
The balls 300 are inserted in both spaces defined by the grooves 130 of the fixed rail 100 and the grooves 230 of the movable rail 200 as stated above, thereby serving to enable the movable rail 200 to move inside the fixed rail 100 in a point-contact manner.
Now, considering the operation of the conventional seat track configured as stated above, first, it is assembled between the bottom plane of a vehicle body and a seat as fastening bolts extending downward from the fixed rail 100 are screwed into the bottom plane of the vehicle body, and the seat is mounted to the upper surface of the movable rail 200. In such an assembled state, when it is desired to move the seat back and forth, as a lever 400 as shown in FIG. 6 is raised so as to allow a latch 420 connected thereto to rotate about a hinge owing to the action of an elastic piece 410, locking protrusions formed at the latch 420 are released from the fitting holes 112 formed at the head portion 111 of the fixed rail 100, thereby allowing the movable rail 200 to be separated from the fixed rail 100. In this separated state, the movable rail 200, which still comes into point contact with the fixed rail 100 by means of the balls 300 inserted in both the spaces between the grooves 130 and 230, moves inside the fixed rail 100 in a sliding manner as a driver or passenger tries to move the seat back and forth on the basis of his/her body size. Then, as the driver or passenger releases the lever 400 at a time when the seat reaches a desired position, the latch 420 rotates downward about the hinge owing to the elastic force of the elastic piece 410, thereby causing the locking protrusions of the latch 420 to be fitted into the fitting holes 112 of the bead portion 111. As a result, the movable rail 200 is fixed inside the fixed rail 100 so as not to move, thus the seat coupled to the movable rail 200 is firmly fixed so as not to move.
The conventional seat track as stated above, however, has a weak point in the locking structure thereof. That is, when any shock is applied to a vehicle from the front or rear-end thereof in case of rear-end or head-on collision, the seat fluctuates due to the shock, thereby being moved back and forth to some extent. As a result, the locking protrusions fitted in the fitting holes 112 formed at the bead portion 111 of the fixed rail 100 are unintentionally released therefrom, resulting in a failure in locking between the fixed rail 100 and the movable rail 200.
Further, since the fixed rail 100 of the seat track is installed on the bottom plane of a vehicle body within a restricted narrow range, the bead portion 111, which must be formed at the fixed rail 100, has a restriction in the overall size thereof, and thus the size and thickness of the locking protrusions to be fitted into the fitting holes 112 of the bead portion 111 should be selected within a restricted range. This results in a deterioration in locking strength.
Furthermore, due to the fact that the bead portion 111 having locking protrusion fitting holes 112 is provided at the fixed rail 100, the manufacture of the fixed rail 100 is inevitably complicated due to the addition of a bead forming process, resulting in a deterioration of workability.